For example, when executing an operation control of a walking assist device assisting walking motions of a human being, or a control of moving motions of a bipedal walking robot, it becomes necessary to successively grasp floor reaction forces acting on leg bodies (specifically, forces acting on ground touching portions of the leg bodies from a floor) of the human being or the bipedal walking robot. By grasping the floor reaction forces, it becomes possible to grasp moments or the like acting on joints of the leg bodies of the bipedal walking moving body and, based on the grasped moments or the like, it becomes possible to determine desired assist forces of the walking assist device, or desired driving torques for the respective joints of the bipedal walking robot or the like.
As a technique of grasping the foregoing floor reaction forces, there has been known one disclosed in, for example, Laid-open Unexamined Patent Publication No. 2000-249570. According to this technique, in view of the fact that a waveform of temporal variation in floor reaction force on each leg body periodically changes during steady walking of a bipedal walking moving body, the floor reaction force on each leg body is grasped as a composite value (linear combination) of a plurality of trigonometric functions having mutually different periods being 1/n (n=1, 2, . . . ) of a walking period. In this case, as a weighting coefficient of each trigonometric function upon combining the plurality of trigonometric functions, there has been used a prescribed value determined in advance per bipedal walking moving body, or a value obtained by adjusting it depending on topography.
However, inasmuch as the foregoing technique aims to grasp the floor reaction forces on the leg bodies with respect to one step or a plurality of steps of the bipedal walking moving body, when a gait of the bipedal walking moving body changes in sequence, it is difficult to accurately grasp the floor reaction forces. Further, for enhancing the accuracy of the floor reaction forces to be grasped, it is necessary to set the foregoing weighting coefficients of the trigonometric functions per bipedal walking moving body, or adjust them depending on topography or the like. Therefore, it is difficult to accurately grasp the floor reaction forces with a reduced influence of environment for movement of the bipedal walking moving body or a difference in individuality of the bipedal walking moving body.
In case of a bipedal walking robot, for example, there has been known one wherein force sensors such as six-axis force sensors are attached to ankle portions or foot portions of respective leg bodies, and floor reaction forces are grasped by outputs of these force sensors. Further, there has also been known a technique of walking a bipedal walking moving body on a force plate placed on a floor, and grasping floor reaction forces by outputs of the force plate.
However, the technique using the force sensors has a disadvantage that when grasping floor reaction forces on leg bodies of particularly a human being, inasmuch as the force sensors should be attached to ankle portions or foot portions of the human being, the force sensors become obstructive to the walking in an ordinary living environment. Further, in case of the one using the force plate, the floor reaction forces can only be grasped in an environment where the force plate is arranged.
The present invention has been made in view of the foregoing background and has an object to provide a floor reaction force estimating method that can accurately grasp floor reaction forces in real time with a relatively simple technique, and that is suitable for grasping floor reaction forces with respect to particularly a human being as a bipedal walking moving body.
Further, it is an object thereof to provide a method of estimating joint moments of the bipedal walking moving body, which can accurately grasp in real time the moments acting on joints such as knee joints of leg bodies by the use of estimated values of the floor reaction forces.